1 # SPDX-License-Identifier: GPL-2.0
11 config LOCKDEP_SUPPORT
14 config STACKTRACE_SUPPORT
17 config RWSEM_GENERIC_SPINLOCK
20 config RWSEM_XCHGADD_ALGORITHM
23 config ARCH_HAS_ILOG2_U32
26 config ARCH_HAS_ILOG2_U64
29 config GENERIC_HWEIGHT
35 config GENERIC_BUG_RELATIVE_POINTERS
38 config ARCH_DMA_ADDR_T_64BIT
41 config GENERIC_LOCKBREAK
42 def_bool y if SMP && PREEMPT
47 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
63 config ARCH_SUPPORTS_UPROBES
68 select ARCH_BINFMT_ELF_STATE
69 select ARCH_HAS_DEVMEM_IS_ALLOWED
70 select ARCH_HAS_ELF_RANDOMIZE
71 select ARCH_HAS_GCOV_PROFILE_ALL
72 select ARCH_HAS_GIGANTIC_PAGE if (MEMORY_ISOLATION && COMPACTION) || CMA
74 select ARCH_HAS_SET_MEMORY
75 select ARCH_HAS_SG_CHAIN
76 select ARCH_HAS_STRICT_KERNEL_RWX
77 select ARCH_HAS_STRICT_MODULE_RWX
78 select ARCH_HAS_UBSAN_SANITIZE_ALL
79 select ARCH_HAVE_NMI_SAFE_CMPXCHG
80 select ARCH_INLINE_READ_LOCK
81 select ARCH_INLINE_READ_LOCK_BH
82 select ARCH_INLINE_READ_LOCK_IRQ
83 select ARCH_INLINE_READ_LOCK_IRQSAVE
84 select ARCH_INLINE_READ_TRYLOCK
85 select ARCH_INLINE_READ_UNLOCK
86 select ARCH_INLINE_READ_UNLOCK_BH
87 select ARCH_INLINE_READ_UNLOCK_IRQ
88 select ARCH_INLINE_READ_UNLOCK_IRQRESTORE
89 select ARCH_INLINE_SPIN_LOCK
90 select ARCH_INLINE_SPIN_LOCK_BH
91 select ARCH_INLINE_SPIN_LOCK_IRQ
92 select ARCH_INLINE_SPIN_LOCK_IRQSAVE
93 select ARCH_INLINE_SPIN_TRYLOCK
94 select ARCH_INLINE_SPIN_TRYLOCK_BH
95 select ARCH_INLINE_SPIN_UNLOCK
96 select ARCH_INLINE_SPIN_UNLOCK_BH
97 select ARCH_INLINE_SPIN_UNLOCK_IRQ
98 select ARCH_INLINE_SPIN_UNLOCK_IRQRESTORE
99 select ARCH_INLINE_WRITE_LOCK
100 select ARCH_INLINE_WRITE_LOCK_BH
101 select ARCH_INLINE_WRITE_LOCK_IRQ
102 select ARCH_INLINE_WRITE_LOCK_IRQSAVE
103 select ARCH_INLINE_WRITE_TRYLOCK
104 select ARCH_INLINE_WRITE_UNLOCK
105 select ARCH_INLINE_WRITE_UNLOCK_BH
106 select ARCH_INLINE_WRITE_UNLOCK_IRQ
107 select ARCH_INLINE_WRITE_UNLOCK_IRQRESTORE
108 select ARCH_SAVE_PAGE_KEYS if HIBERNATION
109 select ARCH_SUPPORTS_ATOMIC_RMW
110 select ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT
111 select ARCH_SUPPORTS_NUMA_BALANCING
112 select ARCH_USE_BUILTIN_BSWAP
113 select ARCH_USE_CMPXCHG_LOCKREF
114 select ARCH_WANTS_DYNAMIC_TASK_STRUCT
115 select ARCH_WANTS_PROT_NUMA_PROT_NONE
116 select ARCH_WANTS_UBSAN_NO_NULL
117 select ARCH_WANT_IPC_PARSE_VERSION
118 select BUILDTIME_EXTABLE_SORT
119 select CLONE_BACKWARDS2
120 select DYNAMIC_FTRACE if FUNCTION_TRACER
121 select GENERIC_CLOCKEVENTS
122 select GENERIC_CPU_AUTOPROBE
123 select GENERIC_CPU_DEVICES if !SMP
124 select GENERIC_FIND_FIRST_BIT
125 select GENERIC_SMP_IDLE_THREAD
126 select GENERIC_TIME_VSYSCALL
127 select HAVE_ALIGNED_STRUCT_PAGE if SLUB
128 select HAVE_ARCH_AUDITSYSCALL
129 select HAVE_ARCH_JUMP_LABEL
130 select CPU_NO_EFFICIENT_FFS if !HAVE_MARCH_Z9_109_FEATURES
131 select HAVE_ARCH_SECCOMP_FILTER
132 select HAVE_ARCH_SOFT_DIRTY
133 select HAVE_ARCH_TRACEHOOK
134 select HAVE_ARCH_TRANSPARENT_HUGEPAGE
135 select HAVE_EBPF_JIT if PACK_STACK && HAVE_MARCH_Z196_FEATURES
136 select HAVE_CMPXCHG_DOUBLE
137 select HAVE_CMPXCHG_LOCAL
138 select HAVE_COPY_THREAD_TLS
139 select HAVE_DEBUG_KMEMLEAK
140 select HAVE_DMA_API_DEBUG
141 select HAVE_DMA_CONTIGUOUS
143 select HAVE_DYNAMIC_FTRACE
144 select HAVE_DYNAMIC_FTRACE_WITH_REGS
145 select HAVE_EFFICIENT_UNALIGNED_ACCESS
146 select HAVE_EXIT_THREAD
147 select HAVE_FTRACE_MCOUNT_RECORD
148 select HAVE_FUNCTION_GRAPH_TRACER
149 select HAVE_FUNCTION_TRACER
150 select HAVE_FUTEX_CMPXCHG if FUTEX
151 select HAVE_KERNEL_BZIP2
152 select HAVE_KERNEL_GZIP
153 select HAVE_KERNEL_LZ4
154 select HAVE_KERNEL_LZMA
155 select HAVE_KERNEL_LZO
156 select HAVE_KERNEL_XZ
158 select HAVE_KRETPROBES
160 select HAVE_LIVEPATCH
162 select HAVE_MEMBLOCK_NODE_MAP
163 select HAVE_MEMBLOCK_PHYS_MAP
164 select HAVE_MOD_ARCH_SPECIFIC
166 select HAVE_PERF_EVENTS
167 select HAVE_REGS_AND_STACK_ACCESS_API
168 select HAVE_SYSCALL_TRACEPOINTS
169 select HAVE_VIRT_CPU_ACCOUNTING
170 select MODULES_USE_ELF_RELA
173 select OLD_SIGSUSPEND3
175 select SYSCTL_EXCEPTION_TRACE
176 select THREAD_INFO_IN_TASK
178 select VIRT_CPU_ACCOUNTING
179 select ARCH_HAS_SCALED_CPUTIME
184 config SCHED_OMIT_FRAME_POINTER
187 config PGTABLE_LEVELS
191 source "init/Kconfig"
193 source "kernel/Kconfig.freezer"
195 source "kernel/livepatch/Kconfig"
197 menu "Processor type and features"
199 config HAVE_MARCH_Z900_FEATURES
202 config HAVE_MARCH_Z990_FEATURES
204 select HAVE_MARCH_Z900_FEATURES
206 config HAVE_MARCH_Z9_109_FEATURES
208 select HAVE_MARCH_Z990_FEATURES
210 config HAVE_MARCH_Z10_FEATURES
212 select HAVE_MARCH_Z9_109_FEATURES
214 config HAVE_MARCH_Z196_FEATURES
216 select HAVE_MARCH_Z10_FEATURES
218 config HAVE_MARCH_ZEC12_FEATURES
220 select HAVE_MARCH_Z196_FEATURES
222 config HAVE_MARCH_Z13_FEATURES
224 select HAVE_MARCH_ZEC12_FEATURES
226 config HAVE_MARCH_Z14_FEATURES
228 select HAVE_MARCH_Z13_FEATURES
231 prompt "Processor type"
235 bool "IBM zSeries model z800 and z900"
236 select HAVE_MARCH_Z900_FEATURES
238 Select this to enable optimizations for model z800/z900 (2064 and
239 2066 series). This will enable some optimizations that are not
240 available on older ESA/390 (31 Bit) only CPUs.
243 bool "IBM zSeries model z890 and z990"
244 select HAVE_MARCH_Z990_FEATURES
246 Select this to enable optimizations for model z890/z990 (2084 and
247 2086 series). The kernel will be slightly faster but will not work
252 select HAVE_MARCH_Z9_109_FEATURES
254 Select this to enable optimizations for IBM System z9 (2094 and
255 2096 series). The kernel will be slightly faster but will not work
259 bool "IBM System z10"
260 select HAVE_MARCH_Z10_FEATURES
262 Select this to enable optimizations for IBM System z10 (2097 and
263 2098 series). The kernel will be slightly faster but will not work
267 bool "IBM zEnterprise 114 and 196"
268 select HAVE_MARCH_Z196_FEATURES
270 Select this to enable optimizations for IBM zEnterprise 114 and 196
271 (2818 and 2817 series). The kernel will be slightly faster but will
272 not work on older machines.
275 bool "IBM zBC12 and zEC12"
276 select HAVE_MARCH_ZEC12_FEATURES
278 Select this to enable optimizations for IBM zBC12 and zEC12 (2828 and
279 2827 series). The kernel will be slightly faster but will not work on
283 bool "IBM z13s and z13"
284 select HAVE_MARCH_Z13_FEATURES
286 Select this to enable optimizations for IBM z13s and z13 (2965 and
287 2964 series). The kernel will be slightly faster but will not work on
292 select HAVE_MARCH_Z14_FEATURES
294 Select this to enable optimizations for IBM z14 (3906 series).
295 The kernel will be slightly faster but will not work on older
300 config MARCH_Z900_TUNE
301 def_bool TUNE_Z900 || MARCH_Z900 && TUNE_DEFAULT
303 config MARCH_Z990_TUNE
304 def_bool TUNE_Z990 || MARCH_Z990 && TUNE_DEFAULT
306 config MARCH_Z9_109_TUNE
307 def_bool TUNE_Z9_109 || MARCH_Z9_109 && TUNE_DEFAULT
309 config MARCH_Z10_TUNE
310 def_bool TUNE_Z10 || MARCH_Z10 && TUNE_DEFAULT
312 config MARCH_Z196_TUNE
313 def_bool TUNE_Z196 || MARCH_Z196 && TUNE_DEFAULT
315 config MARCH_ZEC12_TUNE
316 def_bool TUNE_ZEC12 || MARCH_ZEC12 && TUNE_DEFAULT
318 config MARCH_Z13_TUNE
319 def_bool TUNE_Z13 || MARCH_Z13 && TUNE_DEFAULT
321 config MARCH_Z14_TUNE
322 def_bool TUNE_Z14 || MARCH_Z14 && TUNE_DEFAULT
325 prompt "Tune code generation"
328 Cause the compiler to tune (-mtune) the generated code for a machine.
329 This will make the code run faster on the selected machine but
330 somewhat slower on other machines.
331 This option only changes how the compiler emits instructions, not the
332 selection of instructions itself, so the resulting kernel will run on
338 Tune the generated code for the target processor for which the kernel
342 bool "IBM zSeries model z800 and z900"
345 bool "IBM zSeries model z890 and z990"
351 bool "IBM System z10"
354 bool "IBM zEnterprise 114 and 196"
357 bool "IBM zBC12 and zEC12"
372 prompt "Kernel support for 31 bit emulation"
373 select COMPAT_BINFMT_ELF if BINFMT_ELF
374 select ARCH_WANT_OLD_COMPAT_IPC
375 select COMPAT_OLD_SIGACTION
378 Select this option if you want to enable your system kernel to
379 handle system-calls from ELF binaries for 31 bit ESA. This option
380 (and some other stuff like libraries and such) is needed for
381 executing 31 bit applications. It is safe to say "Y".
383 config SYSVIPC_COMPAT
384 def_bool y if COMPAT && SYSVIPC
388 prompt "Symmetric multi-processing support"
390 This enables support for systems with more than one CPU. If you have
391 a system with only one CPU, like most personal computers, say N. If
392 you have a system with more than one CPU, say Y.
394 If you say N here, the kernel will run on uni- and multiprocessor
395 machines, but will use only one CPU of a multiprocessor machine. If
396 you say Y here, the kernel will run on many, but not all,
397 uniprocessor machines. On a uniprocessor machine, the kernel
398 will run faster if you say N here.
400 See also the SMP-HOWTO available at
401 <http://www.tldp.org/docs.html#howto>.
403 Even if you don't know what to do here, say Y.
406 int "Maximum number of CPUs (2-512)"
411 This allows you to specify the maximum number of CPUs which this
412 kernel will support. The maximum supported value is 512 and the
413 minimum value which makes sense is 2.
415 This is purely to save memory - each supported CPU adds
416 approximately sixteen kilobytes to the kernel image.
420 prompt "Support for hot-pluggable CPUs"
423 Say Y here to be able to turn CPUs off and on. CPUs
424 can be controlled through /sys/devices/system/cpu/cpu#.
425 Say N if you want to disable CPU hotplug.
427 # Some NUMA nodes have memory ranges that span
428 # other nodes. Even though a pfn is valid and
429 # between a node's start and end pfns, it may not
430 # reside on that node. See memmap_init_zone()
431 # for details. <- They meant memory holes!
432 config NODES_SPAN_OTHER_NODES
437 depends on SMP && SCHED_TOPOLOGY
442 This option adds NUMA support to the kernel.
444 An operation mode can be selected by appending
445 numa=<method> to the kernel command line.
447 The default behaviour is identical to appending numa=plain to
448 the command line. This will create just one node with all
449 available memory and all CPUs in it.
452 int "Maximum NUMA nodes (as a power of 2)"
457 Specify the maximum number of NUMA nodes available on the target
458 system. Increases memory reserved to accommodate various tables.
460 menu "Select NUMA modes"
464 bool "NUMA emulation"
467 Numa emulation mode will split the available system memory into
468 equal chunks which then are distributed over the configured number
469 of nodes in a round-robin manner.
471 The number of fake nodes is limited by the number of available memory
472 chunks (i.e. memory size / fake size) and the number of supported
475 The CPUs are assigned to the nodes in a way that partially respects
476 the original machine topology (if supported by the machine).
477 Fair distribution of the CPUs is not guaranteed.
480 hex "NUMA emulation memory chunk size"
482 range 0x400000 0x100000000
485 Select the default size by which the memory is chopped and then
486 assigned to emulated NUMA nodes.
488 This can be overridden by specifying
492 on the kernel command line where also suffixes K, M, G, and T are
509 config SCHED_TOPOLOGY
511 prompt "Topology scheduler support"
518 Topology scheduler support improves the CPU scheduler's decision
519 making when dealing with machines that have multi-threading,
520 multiple cores or multiple books.
522 source kernel/Kconfig.preempt
524 source kernel/Kconfig.hz
528 prompt "s390 architectural random number generation API"
530 Enable the s390 architectural random number generation API
531 to provide random data for all consumers within the Linux
534 When enabled the arch_random_* functions declared in linux/random.h
535 are implemented. The implementation is based on the s390 CPACF
536 instruction subfunction TRNG which provides a real true random
545 config ARCH_SPARSEMEM_ENABLE
547 select SPARSEMEM_VMEMMAP_ENABLE
548 select SPARSEMEM_VMEMMAP
550 config ARCH_SPARSEMEM_DEFAULT
553 config ARCH_SELECT_MEMORY_MODEL
556 config ARCH_ENABLE_MEMORY_HOTPLUG
557 def_bool y if SPARSEMEM
559 config ARCH_ENABLE_MEMORY_HOTREMOVE
562 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
565 config FORCE_MAX_ZONEORDER
571 config MAX_PHYSMEM_BITS
572 int "Maximum size of supported physical memory in bits (42-53)"
576 This option specifies the maximum supported size of physical memory
577 in bits. Supported is any size between 2^42 (4TB) and 2^53 (8PB).
578 Increasing the number of bits also increases the kernel image size.
579 By default 46 bits (64TB) are supported.
583 prompt "Pack kernel stack"
585 This option enables the compiler option -mkernel-backchain if it
586 is available. If the option is available the compiler supports
587 the new stack layout which dramatically reduces the minimum stack
588 frame size. With an old compiler a non-leaf function needs a
589 minimum of 96 bytes on 31 bit and 160 bytes on 64 bit. With
590 -mkernel-backchain the minimum size drops to 16 byte on 31 bit
591 and 24 byte on 64 bit.
593 Say Y if you are unsure.
597 prompt "Detect kernel stack overflow"
599 This option enables the compiler option -mstack-guard and
600 -mstack-size if they are available. If the compiler supports them
601 it will emit additional code to each function prolog to trigger
602 an illegal operation if the kernel stack is about to overflow.
604 Say N if you are unsure.
607 int "Size of the guard area (128-1024)"
609 depends on CHECK_STACK
612 This allows you to specify the size of the guard area at the lower
613 end of the kernel stack. If the kernel stack points into the guard
614 area on function entry an illegal operation is triggered. The size
615 needs to be a power of 2. Please keep in mind that the size of an
616 interrupt frame is 184 bytes for 31 bit and 328 bytes on 64 bit.
617 The minimum size for the stack guard should be 256 for 31 bit and
620 config WARN_DYNAMIC_STACK
622 prompt "Emit compiler warnings for function with dynamic stack usage"
624 This option enables the compiler option -mwarn-dynamicstack. If the
625 compiler supports this options generates warnings for functions
626 that dynamically allocate stack space using alloca.
628 Say N if you are unsure.
636 prompt "QDIO support"
638 This driver provides the Queued Direct I/O base support for
641 To compile this driver as a module, choose M here: the
642 module will be called qdio.
655 config PCI_NR_FUNCTIONS
656 int "Maximum number of PCI functions (1-4096)"
660 This allows you to specify the maximum number of PCI functions which
661 this kernel will support.
663 source "drivers/pci/Kconfig"
676 config NEED_SG_DMA_LENGTH
679 config NEED_DMA_MAP_STATE
684 prompt "Support for CHSC subchannels"
686 This driver allows usage of CHSC subchannels. A CHSC subchannel
687 is usually present on LPAR only.
688 The driver creates a device /dev/chsc, which may be used to
689 obtain I/O configuration information about the machine and
690 to issue asynchronous chsc commands (DANGEROUS).
691 You will usually only want to use this interface on a special
692 LPAR designated for system management.
694 To compile this driver as a module, choose M here: the
695 module will be called chsc_sch.
701 prompt "SCM bus driver"
703 Bus driver for Storage Class Memory.
707 prompt "Support for EADM subchannels"
710 This driver allows usage of EADM subchannels. EADM subchannels act
711 as a communication vehicle for SCM increments.
713 To compile this driver as a module, choose M here: the
714 module will be called eadm_sch.
718 prompt "Support for VFIO-CCW subchannels"
719 depends on S390_CCW_IOMMU && VFIO_MDEV
721 This driver allows usage of I/O subchannels via VFIO-CCW.
723 To compile this driver as a module, choose M here: the
724 module will be called vfio_ccw.
731 bool "kernel crash dumps"
735 Generate crash dump after being started by kexec.
736 Crash dump kernels are loaded in the main kernel with kexec-tools
737 into a specially reserved region and then later executed after
738 a crash by kdump/kexec.
739 Refer to <file:Documentation/s390/zfcpdump.txt> for more details on this.
740 This option also enables s390 zfcpdump.
741 See also <file:Documentation/s390/zfcpdump.txt>
745 menu "Executable file formats / Emulations"
747 source "fs/Kconfig.binfmt"
751 prompt "Enable seccomp to safely compute untrusted bytecode"
754 This kernel feature is useful for number crunching applications
755 that may need to compute untrusted bytecode during their
756 execution. By using pipes or other transports made available to
757 the process as file descriptors supporting the read/write
758 syscalls, it's possible to isolate those applications in
759 their own address space using seccomp. Once seccomp is
760 enabled via /proc/<pid>/seccomp, it cannot be disabled
761 and the task is only allowed to execute a few safe syscalls
762 defined by each seccomp mode.
768 menu "Power Management"
770 config ARCH_HIBERNATION_POSSIBLE
773 source "kernel/power/Kconfig"
785 source "drivers/Kconfig"
789 source "arch/s390/Kconfig.debug"
791 source "security/Kconfig"
793 source "crypto/Kconfig"
797 menu "Virtualization"
801 prompt "Pseudo page fault support"
803 Select this option, if you want to use PFAULT pseudo page fault
804 handling under VM. If running native or in LPAR, this option
805 has no effect. If your VM does not support PFAULT, PAGEEX
806 pseudo page fault handling will be used.
807 Note that VM 4.2 supports PFAULT but has a bug in its
808 implementation that causes some problems.
809 Everybody who wants to run Linux under VM != VM4.2 should select
813 bool "VM shared kernel support"
814 depends on !JUMP_LABEL
816 Select this option, if you want to share the text segment of the
817 Linux kernel between different VM guests. This reduces memory
818 usage with lots of guests but greatly increases kernel size.
819 Also if a kernel was IPL'ed from a shared segment the kexec system
821 You should only select this option if you know what you are
822 doing and want to exploit this feature.
826 prompt "Cooperative memory management"
828 Select this option, if you want to enable the kernel interface
829 to reduce the memory size of the system. This is accomplished
830 by allocating pages of memory and put them "on hold". This only
831 makes sense for a system running under VM where the unused pages
832 will be reused by VM for other guest systems. The interface
833 allows an external monitor to balance memory of many systems.
834 Everybody who wants to run Linux under VM should select this
839 prompt "IUCV special message interface to cooperative memory management"
840 depends on CMM && (SMSGIUCV=y || CMM=SMSGIUCV)
842 Select this option to enable the special message interface to
843 the cooperative memory management.
847 prompt "Linux - VM Monitor Stream, base infrastructure"
850 This provides a kernel interface for creating and updating z/VM APPLDATA
851 monitor records. The monitor records are updated at certain time
852 intervals, once the timer is started.
853 Writing 1 or 0 to /proc/appldata/timer starts(1) or stops(0) the timer,
854 i.e. enables or disables monitoring on the Linux side.
855 A custom interval value (in seconds) can be written to
856 /proc/appldata/interval.
858 Defaults are 60 seconds interval and timer off.
859 The /proc entries can also be read from, showing the current settings.
863 prompt "Monitor memory management statistics"
864 depends on APPLDATA_BASE && VM_EVENT_COUNTERS
866 This provides memory management related data to the Linux - VM Monitor
867 Stream, like paging/swapping rate, memory utilisation, etc.
868 Writing 1 or 0 to /proc/appldata/memory creates(1) or removes(0) a z/VM
869 APPLDATA monitor record, i.e. enables or disables monitoring this record
873 The /proc entry can also be read from, showing the current settings.
875 This can also be compiled as a module, which will be called
880 prompt "Monitor OS statistics"
881 depends on APPLDATA_BASE
883 This provides OS related data to the Linux - VM Monitor Stream, like
884 CPU utilisation, etc.
885 Writing 1 or 0 to /proc/appldata/os creates(1) or removes(0) a z/VM
886 APPLDATA monitor record, i.e. enables or disables monitoring this record
890 This can also be compiled as a module, which will be called
893 config APPLDATA_NET_SUM
895 prompt "Monitor overall network statistics"
896 depends on APPLDATA_BASE && NET
898 This provides network related data to the Linux - VM Monitor Stream,
899 currently there is only a total sum of network I/O statistics, no
901 Writing 1 or 0 to /proc/appldata/net_sum creates(1) or removes(0) a z/VM
902 APPLDATA monitor record, i.e. enables or disables monitoring this record
906 This can also be compiled as a module, which will be called
911 prompt "s390 hypervisor file system support"
912 select SYS_HYPERVISOR
914 This is a virtual file system intended to provide accounting
915 information in an s390 hypervisor environment.
917 source "arch/s390/kvm/Kconfig"
921 prompt "s390 support for virtio devices"
923 select VIRTUALIZATION
925 select VIRTIO_CONSOLE
927 Enabling this option adds support for virtio based paravirtual device
930 Select this option if you want to run the kernel as a guest under
933 config S390_GUEST_OLD_TRANSPORT
935 prompt "Guest support for old s390 virtio transport (DEPRECATED)"
936 depends on S390_GUEST
938 Enable this option to add support for the old s390-virtio
939 transport (i.e. virtio devices NOT based on virtio-ccw). This
940 type of virtio devices is only available on the experimental
941 kuli userspace or with old (< 2.6) qemu. If you are running
942 with a modern version of qemu (which supports virtio-ccw since
943 1.4 and uses it by default since version 2.4), you probably won't